The objective of this project is a detailed understanding of the initial processes involved in vision. Topics of current study are: 1) Spectroscopic characterization of vertebrate visual pigments in isolated photoreceptors. 2) Theoretical studies aimed at the elucidation of the spectroscopic changes following light absorption, and of the molecular changes leading to cellular excitation. 3) Spectroscopic study of invertebrate visual pigments. 4) Absorption spectroscopy of biological pigments in isolated cells: hemoglobins, hemocyanins and cytochromes.